Chapitre V : partie expérimentale
V- 3 : Constantes physiques et données spectrales des composés isolés
CH2Cl2 / MeOH (65 : 35) pour conduire à l’état pur le composé VR9 (9 mg) .
La fraction Fr10 :
La fraction Fr10 (68mg) contient un produit majoritaire qui a précipité dans MeOH. Ce dernier est lavé plusieurs fois au méthanol pour donner le composé VR10 (25mg).
V-3 Constantes physiques et données spectrales des composés isolés
Composé VR1 Isoscutellarein7-O-(6’’’-O-acetyl--D-allopyranosyl- (1→2)]--D-glucopyranoside
Formule brute : C27H31O17 poudre jaune
627 g/mol
MS : ESI (mode positif) m/z : 650,019 [M+Na]+
RMN 1H (400 MHz) et RMN 13C (125 MHz) dans (CD3OD)
(Tableau III-2, pages 66)
Composé VR2 Isoscutellarein-7-O -β-D-glucopyranoside
Formule brute : C21H20O11 poudre jaune
436 g/mol
MS : ESI (mode positif) m/z : 471,009 [M+Na]+
RMN 1H (500 MHz) et RMN 13C (125 MHz) dans (DMSO)
(Tableau III-3 pages 72)
Composé VR3 Isoscutellarein-8-O -β-D-glucopyranoside
Formule brute : C21H20O11 poudre jaune
436 g/mol
RMN 1H (400 MHz) et RMN 13C (125 MHz) dans (DMSO)
(Tableau III-4, pages 77)
Composé VR4 Isoscutellareine
Formule brute : C15H10O6 poudre jaune
286.239 g/mol
MS : ESI (mode négatif) m/z : 285,1729 [M-H]-
RMN 1H (500 MHz) et RMN 13C (125 MHz) dans CD3OD)
(Tableau III-5, pages 81)
Composé VR5 apigenin-7-O--glucopyranoside
Formule brute : C21H20O10 poudre jaune
432.4 g/mol
MS : ESI (mode positif) m/z : 455,09 [M+Na]+
RMN 1H (500 MHz) et RMN 13C (125 MHz) dans (CD3OD) (Tableau III-6, pages 85)
Composé VR6 Luteolin-7-O-Glucoside Formule brute : C21H20O11
poudre jaune
448,37g/mol
MS : ESI (mode positif) m/z : 471 [M+Na]+
RMN 1H (500 MHz) et RMN 13C (125 MHz) dans CD3OD) (Tableau III-7, pages 93)
Composé VR7 Luteoline
Formule brute : C15H10O6 poudre jaune
286,24 g/mol
MS : ESI (mode positif) m/z : 286, 0810 [M+].
RMN 1H (500 MHz) et RMN 13C (150 MHz) dans (CD3OD)
(tableau III-8, page 96)
Composé 8 Ajugol
Formule brute : C15H24O9 poudre jaune
348,345g/mol
MS : ESI (mode positif) m/z : 371.342 [M+Na]+
RMN 1H (500 MHz) et RMN 13C (150 MHz) dans CD3OD) (Tableau III-9, pages 104)
Composé VR9 Macfadeonoside Formule brute : C15H22O11
poudre blanche 378,33 g/mol
RMN 1H (500 MHz) et RMN 13C (150 MHz) dans CD3OD) (Tableau III-10, pages 112) Composé VR10 Mannitol Formule brute : C6H14O6 poudre blanche 182 g/mol
MS : ESI (mode positif) m/z : 205,0 [M+Na]+ RMN 1H (500 MHz) et RMN 13C (150 MHz) dans (DMSO) (Tableau III-11, pages 116)
Conclusion générale
Ce travail de thèse avait pour objectif d’isoler, d’identifier les métabolites secondaires et d’évaluer les activités anti oxydantes et anti corrosion de Veronica rosea, une espèce appartenant à la famille des Plantaginacées et qui n’a jamais fait l’objet d’études phytochimiques ni biologiques auparavant.
Après extraction hydroalcoolique des parties aériennes, on procède à la concentration des extraits hydroalcoolique et leurs affrontements par l’éther de pétrole, l’acétate d’éthyle et le n-butanol successivement.
Nous soumettons ensuite l’extrait butanolique obtenu aux différentes techniques de séparation notamment la chromatographie sur colonne de gel de silice. Les structures des produits isolés sont déterminées grâce à l’utilisation des différentes méthodes spectrales à savoir la spectrophotométrie UV-Visible, la RMN1D (1H et 13C), RMN 2D (HSQC, HMBC, COSY), la spectrométrie de masse, mesure du pouvoir rotatoire puis par comparaison des données récoltées avec les données de la littérature.
L’étude phytochimique menée a permis l’obtention et l’identification de dix produits. Il s’agit de sept flavonoïdes, deux iridoïdes et un sucre. Ils se repartissent comme suit :
- Isoscutellareine 7-O- [6-O-acétyl-β-D -allopyranosyl- (1 → 2)] - β-D-glucopyranoside - Isoscutellarein-7-O -β-D-glucopyranoside - Isoscutellarein-8-O -β-D-glucopyranoside - Isoscutellareine - Apigéniné-7-O-β-glucopyranoside - Lutéoline - Luteolin-7-O-Glucoside - Macfadienoside - Ajugol - Mannitol
La présence majoritaire des flavonoïdes et iridoïdes est en parfait accord avec les études phytochimiques antérieures effectuées sur les plantes du genre Veronica. Ces métabolites secondaires sont des marqueurs chimiotaxonomiques de ce genre.
Vu la richesse de l’espèce Veronica rosea en flavonoïdes, nous avons évalué in vitro l’activité anti oxydante de l’extrait n-butanolique par l’utilisation du test scavenger de DPPH.
Les résultats obtenus indiquent que l’extrait testé manifeste un pouvoir anti oxydant significatif (IC50= 45,17± 0,18).
En outre, cet extrait n-butanolique a montré une excellente activité inhibitrice de corrosion du cuivre dans une solution de HNO3 (IE=94.36%).
Pour la suite, Il est souhaitable de mener une étude phytochimique complémentaires sur la partie des racines, et d’évaluer d’autres activités biologiques in vitro et in vivo de cette espèce.
Les structures des composés isolés s’établissent comme suit :
VR1 : Isoscutellareine 7-O- [6-O-acétyl-β-D - allopyranosyl- (1 → 2)] - β-D-glucopyranoside
VR2 : Isoscutellarein-7-O -β-D- glucopyranoside
VR3 : Isoscutellarein-8-O -β-D-glucopyranoside VR4 : Isoscutellareine
O HO OH O OH OH H 2 3 4 5 6 7 8 9 10 1' 2' 3' 4' 5' 6' VR7 : Luteoline VR9 : macfadienoside VR8 : Ajugol VR10 : Mannitol
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Phytochemical compounds and anti-corrosion
activity of Veronica rosea
Rachid Ouache, Hassina Harkat, Patrick Pale & Kafia Oulmi
To cite this article: Rachid Ouache, Hassina Harkat, Patrick Pale & Kafia Oulmi (2018):
Phytochemical compounds and anti-corrosion activity of Veronica rosea, Natural Product Research, DOI: 10.1080/14786419.2018.1474464
To link to this article: https://doi.org/10.1080/14786419.2018.1474464
View supplementary material
Published online: 16 May 2018.
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SHORT COMMUNICATION
Phytochemical compounds and anti-corrosion activity of
Veronica rosea
Rachid Ouachea,b, Hassina Harkata, Patrick Palec and Kafia Oulmib
alaboratoire de physio-toxicologie, pathologie cellulaires et moléculaires-biomolécules (lPtPcMB), Faculté
de Médecine, département de Pharmacie, université de Batna-2, Batna, algérie; bFaculté des sciences
de la Matière, département de chimie, université de Batna-1, Batna, algérie; claboratoire de synthèse et
réactivité organiques, associé au cNrs, Institut de chimie de strasbourg uMr 7177, université de strasbourg, strasbourg, France
ABSTRACT
The aim of this work is the phytochemical study of the butanolic extract of the aerial parts of Veronica rosea. Four compounds 1–4 have been isolated using different chromatographic methods. The structures of these compounds were determined by NMR spectral analysis and mass spectroscopy. The adsorption and anticorrosion effects of this extract were investigated towards the corrosion of copper in 1 M HNO3 aqueous by the weight loss technique and potentiodynamic polarization. The results showed that the butanolic extract is a good inhibitor and the inhibition efficiency increases with increasing of concentration of the inhibitor. The adsorption of this extract on the copper specimen surface was spontaneous and obeyed the Langmuir’s adsorption isotherm. Large value of adsorption equilibrium Constant (Kads = 35 L g−1) was obtained. The polarization
experiments confirmed the data obtained by gravimetric weight-loss. Tafel plot of polarization curves indicates that the extract acts as a mixed type inhibitor.
KEYWORDS
Veronica rosea; flavonoids;
green inhibitor; adsorption; copper
ARTICLE HISTORY received 7 January 2018 accepted 6 May 2018
1. Introduction
The genus Veronica (Plantaginaceae), is widely distributed in the temperate zone of both hemispheres, and it is represented by 450 species in the world (López-González et al. 2015). Some of the Veronica species have reported interesting biological activities such as antibac- terial (Živković et al. 2014), antioxidant (Harput et al. 2011), and anti-inflammatory (Beara et al. 2015).
In folk medicine, some Veronica species are used for pulmonary, and gastrointestinal diseases, as well as renal lithiasis (Gründemann et al. 2013). The genus veronica is known for its richness in flavonoid (Albach et al. 2003; Taskova et al. 2008) iridoid (Kroll-Møller et al.
2017) and phenylethanoid metabolites (Kostadinova et al. 2007).
In this work we report the phytochemical study of butanolic extract of the aerial parts as well as the evaluation of the adsorption and the anti-corrosion activity of this extract.
2. Results and discussion
2.1. Plant collection and extraction
2.1.1. Chemical constituents of n-butanol extract
The phytochemical study of butanolic extract of aerial parts of Veronica rosea led to the iso- lation and identification of four compounds. The structures of these compounds (Figure 1) were identified clearly by analysis of 1H-and 13C-NMR, mass spectrometry data and by com- parison with published data. The isolated compounds were identified as apigenin-7-O-β- glucopyranoside 1 (Taskova et al. 2008; Li et al. 2009) Isoscutellarein7-O-β-d-glucopyranoside Figure 1. structures of isolated compounds 1–4.
the anticorrosion activity of butanolic extract was examined. To the best of our knowledge, nothing has been specifically reported on the use of V. rosea extract for the inhibition of copper corrosion in nitric acid (HNO3).
2.2. Anti- corrosion activities 2.2.1. Weight loss measurements
The corrosion rates of metals and alloys can be determined using different electrochemical and non-electrochemical methods (Khadraoui et al. 2014; Fouda et al. 2015) . The weight loss method of monitoring corrosion rate is useful because of its simple application and reliability (Popova et al. 2003). The corrosion rate of copper was studied at the temperature of 293 K in 1 M nitric acid solution in the absence and the presence of butanolic extract of V. rosea (20–300 ppm). The inhibition efficiency (IE%), coverage surface (θ) and corrosion rate (CR) values are summarized in Table 1.
In the absence of inhibitor, the corrosion rate was 1.79 mg cm−2 h−1(17.54 mm/y). After
adding butanolic extract with different concentrations, the corrosion of copper was retarded. The maximum (%IE) values at 300 ppm was 94.36%, which indicates that butanolic extract of V. rosea acts as a good inhibitor for copper corrosion in 1.0 M HNO3.
2.2.2. Adsorption isotherms analysis
The values of coverage surface (θ) for different concentrations of butanolic extract of V. rosea have been used to explain the best isotherm and to determine the adsorption process. Attempts were made to fit (θ) values to various isotherms (Supplementary file), including Langmuir, Langmuir–Freundlich, Frumkin, Temkin and Flory–Huggins isotherms (Koopal
2008; Damaskin et al. Ed. 1971).
In this study, Langmuir adsorption isotherm was found to be suitable for the experimental findings. The best fit of the experimental data was considered acceptable when the corre- lation coefficient was R2 ≥ 0.98.
The negative value of the standard free energy of adsorption and the high value of the adsorption constant indicates a spontaneous adsorption of this organic inhibitor on copper.
2.2.3. Potentiodynamic polarization studies
The cell used for the Potentiodynamic polarization studies, was a conventional three elec- trode system with platinum auxiliary electrode, saturated calomel as reference electrode Table 1. corrosion rate and inhibition efficiency parameters obtained from Weight loss for copper in 1 M hNo3 solution with and without of different concentration of the butanol extract of V. rosea at (293 K).
Conc. (ppm) Weight loss (mg) CR (mg cm−2 h−1) CR (mm/y) IE% θ
Blank 14.2 1.79 17.54 – –
20 9.5 1.20 11.76 33.09 0.330
50 4.0 0.50 4.89 71.18 0.711
100 1.5 0.18 1.76 89.43 0.894
potential (Ecorr), corrosion current (icorr), anodic Tafel constant (βa), cathodic Tafel constant (βc) and IE were calculated and given in Table 2.
Inspection of Table 2 indicates that The inhibition efficiency of this extract is 87.35% . Also, there is significant change in the anodic and cathodic slopes after the addition of the butanolic extract of V. rosea (Figure S7). These Tafel curves indicate that this extract acts as a mixed-type inhibitor.
3. Conclusion
The study of butanolic extract of the aerial parts of V. rosea acts as a good inhibitor for the copper corrosion in 1.0 M HNO3 solution. The analysis of the results obtained shows that the inhibition efficiency increases with the increase of the butanolic extract concentrations. The adsorption of the organic compound of this extract on the copper surface follows the Langmuir model. The important value of Kads (35Lg-1) and the negative value of ΔGads° (−25 kJ/mol) indicates that the adsorption of this extract on copper surface is spontaneous and may be explained by the presence of O atoms and conjugate double bond. Polarization curves demonstrated that the butanolic extract of the aerial parts of V. rosea is a mixed-type inhibitor for copper surface in 1 M HNO3 solution. The results obtained from the different methods are in good agreement.
Supplementary material
Experimental material relating to this article and supporting NMR information are available online.
Acknowledgements
The authors wish to express their acknowledgements to the University of Strasbourg (France), for providing research facilities and technical support and Dr for his help to realised the potentiodynamic polarization studies
Disclosure statement
No potential conflict of interest was reported by the authors.
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Ce travail est consacré à l’étude phytochimique ainsi l’évaluation des activités anti oxydante et anti corrosion des parties aériennes de Veronica rosea, une espèce endémique non étudiée, appartenant à la famille des plantaginacées. Cette famille est connue par sa richesse en divers métabolites secondaires d’un grand intérêt biologique notamment les flavonoïdes et les iridoïdes.
Cette étude a permis l’obtention et l’identification de 10 produits. Il s’agit de sept flavonoïdes, deux iridoïdes et un sucre. La détermination des structures ont été élucidées par les méthodes spectroscopies (RMN, Masse et UV) et par comparaison avec les données de la littérature.
Une investigation de l’activité antioxydant, par la méthode test scavenger de DPPH de l’extrait butanolique, a montré que notre espèce possède un pouvoir anti oxydant significatif. De plus, l’extrait butanolique a manifesté une excellente activité inhibitrice de corrosion du cuivre dans une solution de HNO3
Mots clés : plantaginacées, Veronica rosea, flavonoïdes, iridoïdes, activité antioxydant,
activité anti corrosion.
صخلم ذھ اب متھي لمعلا ا دل ةسار نم ةيئاوھلا ءازجلأا يف لكآتلا تاداضمو ةدسكلأا تاداضم ةطشنأ مييقتو ةيئايميكوتيفلا Veronica rosea ةلئاع ىلا ةيمتنملا و لبق نم اھتسارد متي مل يتلا ، plantaginacées ةلئاعلا هذھ رھتشت ثيح، ا ةيمھلأا تاذ ةيعيبطلا تابكرملا فلتخم ىلع اھترفوب ةصاخ ةريبكلا ةيجولويبل ديوديريلإاو ديونوفلافلا تابكرم . هذھ انتنكم دقل ىلع لوصحلا نم ةساردلا 10 : تابكرم ةعبس لا نم ، ديونوفلاف لاا نم نينثا ير د مت .دحاو ركسو ديو يوينبلا فرعتلا ا ىلع فلتخم ةطساوب تابكرمل ةيفايطملا قرطلا (RMN, Masse et UV) و ةنراقملاب اذك تانايب عم عجارملا . رھظأ ت ةسارد ضم طاشن دا رابتخا ةقيرط ةطساوب ةدسكلأا DPPH ل صلختسم نأ ، لوناتوبلا ةتبنلا هذھل اھل ةيلعف دض ةربتعم ا لولحم يف يساحنلا لكآتلل اًزاتمم اًطبثم اًطاشن لوناتوبلا صلختسم رھظأ ، كلذ ىلإ ةفاضلإاب .ةدسكلأ يضمح 3 HNO . ثحبلا تاملك ،ةدسكلاا دض ةطشنا ،ديوديريلاا ،ديونوفلافلا : plantaginacées ، Veronica rosea .